<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        // let temp, num1 = 10, num2 = 20
        // temp = num2
        // num2 = num1
        // num1 = temp
        // console.log(num1, num2);

        // let name = prompt('请输入你的姓名')
        // let age = prompt('请输入年龄')
        // let sex = prompt('请输入性别')
        // document.write(name, age, sex)

        // let weeks = ['星期一', '星期二', '星期三', '星期四', '星期五', '星期六', '星期日']
        // console.log(weeks[6]);

        let s, r = prompt('请输入圆的半径')
        s = 3.14 * r * r
        document.write('圆的半径是' + s)
    </script>
</body>

</html>